How to export a transparent clip?
Nevermind, figured it out. Turns out I was rendering with the RGB preset instead of RGBA.

EDIT: Expanding upon my explanation: I was getting a brown background whenever I didn't check "use alpha" on my output node. So I checked that and it solved that problem. I was getting a black background on my render images because of my answer stated above. On your render options in the properties tab, right next to the type of file output you have 3 options: BW, RGB, RGBA. I was rendering my images with the RGB preset, which stands for Red Green Blue, instead of RGBA which stands for Red Green Blue Alpha. So it makes sense that it previously wasn't rendering my alpha background.